The present invention relates to a needling machine and an associated feed control method.
The purpose of a needling machine is to mechanically consolidate a fiber fleece coming from a crosslapper or from any other system and passing between two perforated steel plates called a table and a stripper respectively. This fibre fleece is traversed by needles disposed on a support which is generally referred to as a needle board. The stripper is located facing the needle board which is driven with an alternating motion. The needles penetrate successively into the stripper, into the fibre fleece and into the table and they then carry out a reverse motion over a needling period during which the fibre fleece is displaced by a distance called the feed step. Fibre fleeces are driven in the needling machine upstream by an insertion device consisting of a first pair of rollers and downstream of the needling machine by an extraction device comprising a second pair of rollers.
In traditional needling machines, the feed movement of the fibre fleece is intermittent and takes place only when the needles are withdrawn from the product.
Now, a current development in the design of needling machines consists in increasing the striking rates and the speeds of progress of the product though the machines, in order to increase productivity. But the product to be needled is then subjected, at each stop and start of motion, to excessive accelerations which are difficult to control and which can result in degradation of the product.
From DE-A-1 660 776 there are known insertion means and extraction means driven more or less at the rhythm of the needling by means of a differential transmission coupled to the striking device. This method of driving the extraction rollers does not allow an easy and optimal modulation of the extraction speed according to the type of needled product and according to the rank of the needling machine in question in a line of machines.
The purpose of the invention is to overcome these disadvantages by proposing a needling machine which is designed to allow a modulation of the angular velocity of the extraction rollers during each needling period, this modulation being able to be of variable amplitude up to the obtaining of zero angular acceleration.
This purpose is achieved with a needling machine comprising means for needling, according to a variable striking frequency, a fibre fleece generally passing between two perforated steel plates, a first pair of rollers for inserting the fibre fleece between the two plates with an approximately constant insertion speed, a second pair of rollers for extracting the fibre fleece emerging from the plates, means of driving the needling means with a periodic striking motion, control and processing means connected to these needling drive means and electromechanical means for driving the extraction rollers at a variable speed.